Many people use access terminals, such as cell phones and personal digital assistants (PDAs), to communicate with radio access networks, such as cellular wireless networks. These access terminals and access networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless protocol such as Evolution Data Optimized (Ev-DO), perhaps in conformance with one or more industry specifications such as IS-856, Release 0 and IS-856, Revision A. Another protocol that may be used is known as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-2000. Other protocols may be used as well, such as Global System for Mobile Communications (GSM), Time Division Multiple Access (TDMA), and/or any others.
Access networks typically provide services such as voice, Short Message Service (SMS) messaging, and packet-data communication, among others, and typically include a plurality of base stations, each of which provide one or more coverage areas, such as cells and sectors (i.e., individual areas of a cell that allow the cell to carry more calls). When an access terminal is positioned in one of these coverage areas, it can communicate over the air interface with the base station, and in turn over one or more circuit-switched and/or packet-switched signaling and/or transport networks to which the base station provides access.
Access terminals and access networks may conduct communication sessions (e.g. voice calls and data sessions) over a pair of frequencies known as carriers, with a base station of an access network transmitting to an access terminal on one of the frequencies, and the access terminal transmitting to the base station on the other. This is known as frequency division duplex (FDD). A base-station-to-access-terminal link is known as the forward link, while a access-terminal-to-base-station link is known as the reverse link. Each of the base stations may transmit one or more pilot signals to the access terminals via the forward link. The access terminals may use the pilot signals to determine which base stations and/or sectors to use to conduct the communication sessions.